configureMessageConverters

Configure the HttpMessageConverters to use in argument resolvers
and return value handlers that support reading and/or writing to the
body of the request and response. If no message converters are added to
the list, default converters are added instead.

getValidator

Provide a custom Validator instead of the one created by default.
The default implementation, assuming JSR-303 is on the classpath, is:
LocalValidatorFactoryBean.
Leave the return value as null to keep the default.

configureDefaultServletHandling

Configure a handler to delegate unhandled requests by forwarding to the
Servlet container's "default" servlet. A common use case for this is when
the DispatcherServlet is mapped to "/" thus overriding the
Servlet container's default handling of static resources.